Typewriter carriage and ribbon field control for error correction

ABSTRACT

An error correcting typewriter having mechanism for disabling the forward spacing mechanism of the carriage to prevent movement of the carriage for two successive actuations of any character key. A manual key is connected with and to concurrently operate the backspace drive mechanism, the disabling mechanism and the ribbon vibrator. The carriage, after being backspaced one letter width increment, remains in such position during the actuation of a first character key to obliterate an error and the actuation of a second character key to print a correct character. Thereafter, the forward spacing mechanism again becomes effective.

Apr. 24,1973

United States Patent 11 1 Ozimek et a].

[5 1 TYPEWRITER CARRIAGE AND ...197/91 .....l97/91 ......l97/9l ....l97/l8l Wolowitz RIBBON FIELD CONTROL FOR ERROR CORRECTION' [75] -Inventors: Chester E. Ozimek, Park Ridge;

Charles H. Seefeldt, Riverside, both of I11. I

Assigneei Sears, Roebuck and Co.,

Chicago,

Primary Examiner-Ernest T. Wright, Jr.

[22] Filed: Dec. 11,1970 Attorney-Nathan N. Kraus and Joseph R. Marcus [21] App]. No.: 97,169

[57] ABSTRACT An error correcting typewriter having mechanism for disabling the forward spacing mechanism of the car- [52] US. Cl. ......................197/82, 197/91, 197/157,

riage to prevent movement of the carriage for two successive actuations of any character key. A manual key is connected with and to concurrently operate the backspace drive mechanism, the disabling mechanism and the ribbon vibrator. The carriage, after being backspaced one letter width increment, remains in [56] References Cited such position durlng the actuation of a first character UNITED STATES PATENTS key to obliterate an error and the actuation of a Fondiller........ ...l..;.....,,.....

n r 2 2 a a m am n m 5 mm m re om w c H a n m I .1 m w D.S m mm 2 y 1 em 5 m .m r. 6 3 e v I t C C m a 5 m hm he tS .fe d m ne o C w STb 121. mmw mm 777 999W h lll 17 m m m w 3,270,852 9/1966 2,913,091 11/1959 Neumann..... 3,154,183 10/1964 Wolowitz..... 1,905,118 4/1933 Nadell.........-.

640,254 [I 1900 Anderson 1,174,696 3/1916 Patented April 24, 1973 5 Sheets-Sheet 2 Patented A ril 24, 1973 3,729,081

3 Sheets-Sheet 5 F1 6 96 g 10/ H2 FIG, 3

TYPEWRITER CARRIAGE AND RIBBON FIELD CONTROL FOR ERROR CORRECTION BACKGROUND OF THE INVENTION The present invention relates to typewriters and related printing apparatus of the impact or non-impact type including remote input printers and other similar types of apparatus.

More particularly our invention relates to mechanism incorporated in a typewriter or other related printing apparatus which functions to position the printing system of the apparatus at a point where it is desired to print a character and to hold it in such position until de-activated by subsequent action of the apparatus.

SUMMARY OF THE INVENTION The present invention may be embodied in printing apparatus of the types herein described and may be utilized in a number of functions which require retaining the printing system at a print point until the completion of one or more operations. For example, the mechanism of our invention has application to an error correction feature of a typewriter or printing apparatus as will be hereinafter described.

For purposes of explanation only our invention will be described in relation to a typewriter embodying error correction features adapted for use with a composite double striped ribbon, one longitudinal half of which is inked to make character impressions on paper in the usual manner and the other longitudinal half of which carries a pressure transferable opaque adherent pigment which when applied over the error renders it substantially invisible so that a correct character may be imprinted thereon. It will be understood, however, that our invention is not to be limited to the application hereinafter to be described.

Briefly, the typewriter with error correction features embodies a special key operatively connected to mechanism arranged when the key is actuated simultaneously to backspace the carriage one letter space, shift the ribbon field to obliterating position and lock the carriage against forward advance. The key corresponding to the imprinted error is then actuated to obliterate the error and in this operation no movement of the carriage takes place. However, the ribbon shifts to inking or printing position. When the correct character key is actuated the correct character is imprinted and the carriage is caused to advance one letter space as in a conventional manner.

In a modified embodiment there is provided a special obliterating key linked to a typebar carrying a flat face type font instead of a conventional type character. This type font has a face area sufficient to superimpose opaque pigment over the largest of the characters which may be imprinted by the machine. Thus, in order to effect a correction, an operator would always actuate this special obliterating key instead of the key corresponding to the error character. In all other respects, the sequence of operations would be identical with that described above.

In another modified embodiment the typewriter is provided with a special obliterating key and type font, as above described, and mechanism is provided operatively connected to the key so that when the key is depressed the ribbon is automatically shifted to and/or latched in obliterating position and the carriage is locked against advance movement. If the ribbon is shifted and latched in obliterating position the ribbon is returned to print position either by (l) the return movement of the obliterating key or (2) the actuation of the correct character key. Accordingly, in order to effect correction of an error the following sequence of operations is required:

1. The carriage is backspaced one letter space by conventional means.

2. The special obliterating key is depressed to deposit opaque pigment over the imprinted area, and,

3. The correct character key is then struck to imprint the correct character and concurrently therewith the carriage is caused to advance one character space.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic top plan view of a typewriter in accordance with our invention;

FIG. 2 is an exploded perspective view showing the cooperative relationship of the various parts of the invention in the machine;

FIG. 3 is an enlarged fragmentary top plan view, showing certain of the parts of the automatic ribbon field selection mechanism;

FIG. 3a is an elevational view, on an enlarged scale, of the ribbon vibrator.

FIG. 4 is a fragmentary side elevational view on an enlarged scale, of certain of the parts shown in FIG. 2;

FIG. 5 is a top plan view of the escapement control means;

FIG. 6 is a rear elevational view of a detail shown in FIGS;

FIG. 7 is a fragmentary elevational view of a detail of the escapement control means;

FIG. 8 is an elevational view of the escapement latching assembly,

FIG. 9 is a more or less side elevational view illustrating the relationship of a type font to the ribbon when depositing opaque material over an imprinted error;

FIG. 10 is a diagrammatic view showing the steps in the correction of an imprinted error, and

FIG. 11 is a perspective view of a type bar provided with a universal obliterating type font.

BRIEF DESCRIPTION OF A PREFERRED EMBODIMENT Referring to the drawing, the invention is shown as applied to a 'well known make of commercial typewriter and only those parts of the machine which contribute directly to the essentials of the present invention have been'included in the drawing. The numeral 20 designates generally, a typewriter provided with the usual bank of keys 21 manually operable for imprinting characters, a. space bar 22, a platen roller and carriage 22a conventional carriage spacing mechanism, not shown, a backspace key 23 for producing letter width stepwise movements of the carriage 22a in a rearward direction, a ribbon field control selector disc 24, and ribbon carrying spools 26 for inked ribbon 29.

Our invention includes the provision of a special key 27 operatively connected to mechanism performing particular functions, hereinafter to be described.

Referring to FIGS. 2-5, the typewriter 20 is provided with the usual ribbon vibrator 28 carrying a ribbon 29, the upper longitudinal half of which comprises an inking portion 290 while the lower longitudinal half 2912 of which carries opaque obliterating material. Conventionally, the vibrator 28 is connected to a crank 31 operatively connected to a ribbon vibrator link 32 terminating in a hooked end 33 received in a T-slot 34 ofa feed arm 36. When a key 21 is depressed the feed arm 36 which is pivoted, as at 37, is rocked by link 38 in a clock-wise direction, as viewed in FIG. 3, causing the vibrator 28 to move upwardly to bring the inking section portion 29a of the ribbon 29 into printing position. It will be understood that in normal printing operation the hooked end 33 is disposed in the forward end 34a of slot 34. In order to shift the ribbon 29 so that its lower longitudinal half 29b is in registration with the type fonts 80 it is required that the hooked end 33 be shifted to the rearward end 34b of slot 34, substantially to the position illustrated in FIG. 3. Referring to FIGS. 2 and 4, the key 27 is connected by link 39 to an actuating member 41 pivoted as at 42. Said actuating member 14 includes three pierced lobes 41a, b, c and an upwardly extending arm 43 terminating in a laterally bent portion 44. As seen clearly in FIGS. 2 and 4 the link 39 is connected to lobe 41a of the member 41.

A slide member 46 provided with a pair of elongated slots 47 and a depending arm 48 is supported for sliding movement on a frame member 49. The depending arm 48 carries a laterally extending pin 51, for a purpose as will be hereinafter explained. Superposed on the slide 46 for relative sliding movement is a second slide 52 provided with a pair of elongated slots 53 and upstanding integral lugs 54 and 56. The lug 56 is provided with a vertical slot 57, opening upwardly, and has a laterally extending arm 58. A lug 60 depends from an edge of the slide 52. A pair of screws 59 retain the slides 46 and 52 on the frame portion 49. Referring to FIG. 3 it will be seen that the vibrator link 32 is received in the slot 57 and that movement of the slide 52 will affect the positioning of the hooked end 33 within the feed arm slot 34. Referring to FIGS. 3 and 4 the laterally bent portion 44 of the member 41 extends transversely of the lug 54 so that when the member 41 is rocked lug 54 is engaged by laterally bent portion 44 to move slide 52 rearwardly or to the right, as viewed in FIG. 4. A spring 61 secured to the arm 58 and to one of the screws 59 biases the slide 52 forwardly of the machine.

A lever 62 shaped substantially as illustrated in FIGS. 2 and 3 is pivotally supported coaxially with the feed arm 36, as at 37. The lever 62 includes an upstanding lug 63 disposed in close proximity to the feed arm 36 and an arm 64 having an intermediate offset portion providing a shoulder 66. Referring to FIG. 3 it will be seen that the shoulder 66 under certain conditions of operation is adapted to engage the lug 54 to serve as a releasable latch for holding the slide 52 in a position of operation. A spring 67 connected to one end of the lever 62 biases arm 64 into engagement with lug 54. Under certain conditions of operation, as will be hereinafter explained, when the feed arm 36 is caused to rock clock-wise, as viewed in FIG. 3, the edge of the feed arm 36 engages the lug 63 rocking lever 62 clockwise so that the shoulder 66 is moved out of engagement with the lug 54 thereby permitting the slide 52 to move forwardly in the direction urged by spring 61 which correspondingly moves vibrator link 32.

Referring to FIGS. 2 and 4 the member 41 is connected by means of backspace link 68 to the conventional backspace mechanism of the machine which includes a bell crank 69 and a lever 71 connected to the backspacing pawl, not shown. It will be apparent that rocking of the member 41 through the medium of the elements just described will effect backspacing of the carriage 22a one letter space in a conventional manner. The escapement mechanism of the present invention embodies structural features designed to perform the desired functions of the invention. Referring to FIG. 2 there is shown a conventional escapement impeller 76 which is connected by a pin and slot connection 76a through linkage, indicated generally by the number 77, to a space bar 22. The impeller 76 is supported for sliding movement by a pin and slot connection 76b on a frame element 20a and also is connected to a universal bar 79 which is adapted to be engaged by each of the type bars 81. Key 21 is connected to the type bar 81 by a link 83. When a key 21 is depressed the type bar 81 is rocked into engagement with the universal bar 79 connected by means of a crank 84 to the escapement impeller 76 the crank 84 being pivoted, as at 84a and pivotally connected to impeller 76, as at 84b. Thus, as each key 21 or the space bar 22 is actuated the escapement impeller 76 is correspondingly moved. Conventionally, the escapement impeller 76 includes an up standing lug not shown, which is adapted to engage the rigid dog 86 of the escapement mechanism. In the present invention the impeller 76 has secured thereto, as with screws 87a, an upstanding lug 87 with a depending dog 88 which functions, as will be hereinafter described. Referring particularly to FIGS. 5 to 7, our invention includes a novel slide 89 disposed below the escapement impeller 76 and arranged for movement in a direction transverse to the movement of the escapement impeller 76. The slide 89 comprises a generally rectangular plate provided with a pair of elongated slots 91 adapted to receive screws 92 which slideably secure the slide 89 to a suitable support 93. The slide 89 is provided with an elongated rectangular cutout 94. A resilient leaf spring 96 provided with an offset terminal portion 97 is received in the cutout 94 with the terminal portion 97 being secured to the slide 89, as with a screw 98. The main body portion of the spring 96 which is received in the cutout 94 is flush with the top surface of slide 89. The spring 96 is provided with two angular lugs 99 and 101 arranged in spaced relation and struck from one edge of the body thereof. The slide 89 is provided with similarly struck upstanding lugs 102 and 103 along the edge of the cutout 94 adjacent the lugs 99 and 101. The spacings between lugs 99 and 101 and 102 and 103 in the present instance, are identical and each corresponds to a full step of the carriage 22a. It will be understood that the spacings of the lugs 99, 101, 102 and 103 will vary according to the printing dynamics of a particular typewriter 20 or printing apparatus and that the upstroke or backstroke of the type bar 81 will function in cadence with the movement of the printing head or carriage 22a. However, as will be seen by reference to FIG. 5 lugs 99 and 101 are staggered in relation to lugs 102 and 103 so that lug 99 is one-half space from lug 102 and lug 101 is disposed medially of lugs 102 and 103. A spring 104 connected to the slide 89 as at 90 and to a lug 93a on the support 93 biases the slide 89 in a direction to the left, as viewed in FIG. 5. A portion of the rearward edge of slide 89 is cutaway to provide a cam 106 for a purpose as will be hereinafter explained. The cam 106 bears a definite relationship to the location of the lugs 99, 101-103. A flexible cable 107 is secured to one end of the slide 89 and is trained around a pulley 107a, the free end of the cable 107 being secured to the lobe 410 of the member 41, as illustrated in FIGS. 2 and 4. It will be seen that rocking of the member 41 in a clockwise direction, in a manner as will be hereinafter explained, will effect movement of the slide 89 to the right, as viewed in FIG. 5. Referring to FIG. 7 it will be noted that the dog 88 on escapement impeller 76 is in operative alignment with the lugs 99, 101-103 of the slide 89.

A bracket 108 shaped substantially as illustrated in FIG. 2 includes a slotted portion 109 which is adapted to be attached to the conventional bracket, not shown, attached to the carriage rail of the typewriter 20. The conventional bracket carries the escapement mechanism for the typewriter 20. The bracket 108 is provided with an ascending arm 111 and an integral rearwardly extending arm 112 terminating in a bent end lug 113. An actuating member 114 is provided with a longitudinally extending slot 116 and is slideably secured to the face of the arm 112, as with screws 117. The forward end 118 is enlarged and bent angularly and laterally in relation to the plane of the body of member 114 so as to provide a cam follower arranged to engage the cam portion 106 of the slide 89. The member 114 is provided rearwardly with a laterally ex tending portion 119 the rearward edge of which is beveled as at 121. A coil spring 122 hooked between a notch 122a in the rearward edge of the member 114 and one of the screws 117 serves to bias the member 114 in a direction to engage the end 118 with the cam portion 106. Pivotally supported on the ascending arm 111 is a latch member 123 shaped substantially as illustrated in FIGS. 2 and 8. The forward end of said latch member 123 is stepped to provide a shoulder 124 arranged to engage the laterally extending portion 86a of the conventional rigid escapement dog 86 to function as will be hereinafter described. The rearward end of the latch member 123 is provided with a laterally extending portion 126, the forward edge of which is beveled as at 127. A spring 128 connected to the end portion 126 and to the end lug 113 normally biases the latch member 123 so that its left hand end, as viewed in FIG. 8, is maintained in engagement with the laterally bent portion 86a of the escapement dog 86. Referring to FIG. 8, it will be seen that the lateral end portions 119 and 126 are adapted to engage with each other when the activating member 114 is caused to be moved to the right, as viewed in FIG. 8. In such movement the beveled edge 121 functions in the nature of a cam acting on the beveled edge 127 to rock the latch member 123 in a counter-clockwise direction, to release the latching effect of the shoulder 124 on the rigid dog portion 86a, as will be hereinafter explained.

OPERATION The operation of'the above described embodiment of our invention briefly, is as follows:

Assuming that a character has been imprinted in error, the character being the letter f as shown in FIG. 10. In order to effect a correction, the key 27 is depressed to effect rocking of the member 41 in a clockwise direction, as viewed in FIGS. 2 and 4. In such movement the laterally bent position 441 engages the lug S4 of the slide 52 moving the slide 52 rearwardly or the right, as viewed in FIG. 4 so that the vibrator link 32 is correspondingly moved to position the hook end 33 in the rearward portion 34b of slot 34. As the slide 52 moves rearwardly the lug 541 is engaged by the shoulder 66 of lever 64, thereby latching the slide 52 and the vibrator link 32 in the position illustrated in FIG. 3. The vibrator link 32 is now in position for maximum movement. Simultaneously, backspace link 68 connected to member 41 rocks the bell crank 69 in a clockwise direction, as viewed in FIG. 2, drawing lever 71 to the right thereby to backspace the carriage one letter space. Also, the movement of member 41 through the medium of the cable 107 draws the slide 89 to the right, as viewed in FIG. 5, slightly beyond the point at which the dog 88 on escapement impeller 76 will engage the lug 99 on the spring 96. It will be understood that spring 96 will yield to permit lugs 99 and 101 to pass under dog 88.

When key 27 is released spring 104 will tend to draw the slide 89 to the left, as viewed in FIG. 5, so that the I lug 99 engages the dog 88 latching the slide 89 against further movement to the left. The rigid dog 86 of the escapement mechanism is held in locked position by reason of the engagement of the shoulder 124 with the projection 86a of the dog 86. Thus, the carriage 22a is locked against movement 50 that when a character key 21 is depressed no movement of the carriage 22a will take place. The typewriter 20 is now conditioned for the next step in effecting a correction. Upon depressing a key 21 corresponding to the imprinted error character the ribbon 29 is caused to shift upwardly to move the lower half portion 2917 into alignment with the type face 80 of the type bar 81 so that when the type face 80 impinges on the ribbon 29 the opaque material on lower half 29b is deposited over the imprinted error to obliterate the same. On the upstroke of the type bar 81 the escapement impeller 76 is caused to move to the left, as viewed in FIG. 7, whereby the dog 88 is moved out of engagement with the lug 99 and into the path of movement of the lug 102. Thus, the slide 89 is permitted to move one-half space corresponding to the longitudinal distance between lugs 99 and 102. Correspondingly, as the feed arm 36 is caused to move to the right, as viewed in FIG. 3 to shift the ribbon 29 upwardly the righthand edge of the feed arm 36 engages lug 63 of lever 62 causing the lever 62 to pivot in a clockwise direction and moving the shoulder 66 out of engagement with lug 54. The spring 61 now may draw slide 52 forwardly and thereby position the hook 33 of link 32 in the forward portion 34a of slot 34 thereby conditioning the ribbon vibrator 28 so that upon the next actuation of the feed arm 36, as will be hereinafter explained, the inking portion 29a of the ribbon 29 will be disposed in alignment with a type face 80 for imprinting. On the return stroke of the type bar 81 the escapement impeller 76 is caused to move to the right, as viewed in FIG. 7 thereby moving dog 88 out of engagement with lug 102 but in the path of movement of lug 101. Accordingly, slide 89 is permitted to move an additional one-half space. However, no movement of the carriage 22a takes place.

Upon depressing a key 21 corresponding to the correct character, on the upstroke of the type bar 81 the escapement impeller 76 is again caused to move to the left, as viewed in FIG. 7, thereby moving dog 88 out of engagement with the lug 101 and into the path of movement of lug 103. The carriage 22a is caused to move one-half letter space. On the return stroke of the type bar 81 the escapement impeller 76 moves to the right, as viewed in FIG. 7, moving dog 88 out of engagement with lug 103. It will be noted that when .the slide 89 moves from its initial position in which the dog 88 engages the lug 99 to the position in which the dog 88 engages the lug 101, the cam follower 118 is in engagement with the valley portion 106a of the cam 106 and in such position the lateral portion 119 of member 114 is out of engagement with the cooperating lateral portion 126 of the latch member 123. However, in the next step as the slide 89 moves to the left, as viewed in FIG. 5, the follower 118 is caused to ride up on the sloped ramp portion 106b of the cam 106 causing the member 114 to move rearwardly or to the right, as viewed in FIG. 8, whereby the portion 119 engages the portion 126 camming the latter upwardly to rock the lever 123 in a counter clockwise direction, thereby effecting disengagement of the shoulder 124 from the lateral projection 86a of the rigid escapement dog 86 thus permitting the escapement dog 86 to continue to function in the normal manner and permitting the carriage 22a to advance one letter space.

The invention has been described as applied to a typewriter having a particular kind of printing dynamics. However, it will be understood that the invention is not to be limited only to the particular machine described but is applicable to machines having different characteristics of printing dynamics. In the present instance the carriage is caused to move onehalf space on the up-stroke of a type bar 81 and another one-half space on the down stroke of the type bar 81. Other types of typewriters embody different printing dynamics, as for example, on the up-stroke of a type bar 81 some carriages 22a may move one-third of a space and on the down stroke two-thirds of a space or the carriage 22a may move a full space on the upstroke with no movement on the down stroke. The present invention coordinates with printing dynamics of any typewriter so that the carriage 22a is conditioned in accordance with the printing dynamics of the specific typewriter or printing machine to duplicate the print position of the type bar 81 on upstroke.

FIG. 11 illustrates a modified type font 135 carried on type bar 81a and bearing no character but arranged when caused to impinge on the obliterating half portion 29b of the ribbon 29 to deposit over an imprint a layer of opaque material in an area sufficient to cover the largest character. Thus, instead of depressing a key 21 corresponding to an imprinted error to effect obliteration of the same, the key 21 related to the modified type font 135 is utilized for obliteration. In all other respects the sequence of operations is identical with that above described.

In another modified embodiment illustrated in FIG. 2 the ribbon field selector disc 24 which is rotatably supported on a frame member b is connected by means of a link to the slide 46 as at 51. The connection between the link 130 and the disc 24 is in the nature of a crank arrangement so that rotation of the disc 24 will effect longitudinal movement of the slide 46. The depending arm 48 of the slide 46 is disposed forwardly of the depending lug 60 so that as the slide 46 is caused to move rearwardly the arm 48 will engage lug 60 and effect corresponding movement of the slide 52 to position the vibrator link 32 in relation to the feed arm 36 thereby to control the positioning of the ribbon field. The above described mechanism may be utilized to lock the position of the ribbon field in the event that it is desired to obliterate a plurality of imprinted characters. Under normal conditions of operation the slide 46 is disposed in retracted position.

It will be understood that in printing apparatus where our invention is utilized for the printing of accent or related symbols or dead characters or in the justification of a line of printed characters, unrelated to error correction, the ribbon shifting mechanism, hereinabove described, is not incorporated in the printing apparatus, or if incorporated, is temporarily deactivated so that it will not function.

We claim:

1. In a printing apparatus including character printing mechanism, paper support mechanism, spacing means for step-wise moving said paper support mechanism relative to said printing mechanism to accomplish printing of a line of characters, and backspace drive means for step-wise moving said paper support mechanism in a backward direction in letterwidth increments upon successive operations of said backspace drive means, the improvement which comprises means for disabling said spacing means, a manually operable key operatively connected respectively to said backspace drive means and to said disabling means whereby actuation of said key will concurrently backspace said paper support mechanism and disable said spacing means to prevent movement of said paper support mechanism, and means actuated by said character printing mechanism for rendering said disabling means ineffective and said spacing means effective, said spacing means including an escapement and an impeller having a dog and the disabling means including a lever arranged to latch said escapement against movement, a slide member having spaced lugs sequentially engageable by said dog whereby to control the movement of said slide member, cam means associated with said slide member, and means actuated by said cam means to act on said lever to unlatch said escapement to render said spacing means effective.

2. A typewriter for use with a ribbon providing a printing field and a print obliterating field, said ,typewriter including character printing mechanism,

paper support mechanism, spacing means for step-wise moving said paper support mechanism in a forward direction, to accomplish printing ofa line of characters, printing control keys operatively connected to said character printing mechanism, a ribbon vibrator actuated by the printing control keys to bring a ribbon field momentarily into impressing position upon actuation of any one of said printing control keys, backspace drive means for step-wide moving said paper support mechanism in a backward direction in letter width in crements upon successive operations of said backspace drive means, the improvement which comprises means for disabling said spacing means, and a manually operable key operatively connected respectively to said backspace drive means, said ribbon vibrator and said disabling means whereby actuation of said manually operable key will concurrently backspace said paper support mechanism, disable said spacing means to prevent movement of said paper support mechanism and condition said vibrator to move the obliterating field of said ribbon into position to obliterate an imprinted character upon actuation of a printing control key, said spacing means including an escapement and an impeller having a dog and the disabling means including a lever arranged to latch said escapement against movement, a slide member having spaced lugs sequentially engageable by said dog whereby to control the movement of said slide member, cam means associated with said slide member, and means actuated by said cam means to act on said lever to unlatch said escapement to render said spacing means effective.

3. In a printing apparatus including character printing mechanism, paper support mechanism, spacing means for step-wise moving said paper support mechanism relative to said printing mechanism to accomplish printing a line of characters, and means for disabling said spacing means, said spacing means including an escapement and an impeller having a dog, said disabling means including a lever arranged to latch said escapement against movement, a slide member having spaced lugs sequentially engageable by said dog whereby to control the movement of said slide member, cam means associated with said slide membenand means actuated by said cam means to act on said lever to unlatch said, escapement to render said spacing means effective. 7

4. In a printing apparatus including character printing mechanism, paper support mechanism, spacing means for step-wise moving said paper support mechanism to accomplish printing a line of characters, and means for disabling said spacing means, said spacing means including an escapement and an impeller having a dog, said disabling means including a lever arranged to latch said escapement against movement, a slide member comprising a plate having a cut out, a flat spring member received in said cut out, said plate and said spring member having spaced upstanding lugs arranged to be sequentially engageable by said dog whereby to control the movement of said slide member in one direction, said spring member being yieldable so as to permit the lugs thereon to pass under said dog in an opposite direction of movement of said slide member.

5. In an error correcting typewriter comprising character printing mechanism including printing control keys operatively connected to said character printing mechanism, paper support mechanism, spacing means operatively controlled by said printing control keys for step-wise moving said paper support mechanism in a forward direction to accomplish printing of a line of characters, a ribbon providing a printing field and a print obliterating field, a ribbon vibrator actuated by the printing control keys guiding said ribbon to bring a ribbon field momentarily in impressing position, backspace drive means for stepwise moving said paper sugport mechanism iii a backward direction in ct er W1 t increments, the improvement which comprises means for disabling said spacing means to prevent forward movement of said paper support mechanism for two successive actuations of any of said printing control keys, a manually operable key connected with and operable to con-currently operate said backspace drive means, said disabling means and said ribbon vibrator to position the ribbon obliterating field in impressing position, whereby upon the actuation of a first printing control key next following the actuation of said manually operable key a character imprinted in error is obliterated, and means operated by said first printing control key for concurrently conditioning said spacing means and said ribbon vibrator for printing over the obliterated character a correct character upon the actuation of a second printing control key and for rendering said spacing means again effective. 

1. In a printing apparatus including character printing mechanism, paper support mechanism, spacing means for step-wise moving said paper support mechanism relative to said printing mechanism to accomplish printing of a line of characters, and backspace drive means for step-wise moving said paper support mechanism in a backward direction in letter-width increments upon successive operations of said backspace drive means, the improvement which comprises means for disabling said spacing means, a manually operable key operatively connected respectively to said backspace drive means and to said disabling means whereby actuation of said key will concurrently backspace said paper support mechanism and disable said spacing means to prevent movement of said paper support mechanism, and means actuated by said character printing mechanism for rendering said disabling means ineffective and said spacing means effective, said spacing means including an escapement and an impeller having a dog and the disabling means including a lever arranged to latch said escapement against movement, a slide member having spaced lugs sequentially engageable by said dog whereby to control the movement of said slide member, cam means associated with said slide member, and means actuated by said cam means to act on said lever to unlatch said escapement to render said spacing means effective.
 2. A typewriter for use with a ribbon prOviding a printing field and a print obliterating field, said typewriter including character printing mechanism, paper support mechanism, spacing means for step-wise moving said paper support mechanism in a forward direction, to accomplish printing of a line of characters, printing control keys operatively connected to said character printing mechanism, a ribbon vibrator actuated by the printing control keys to bring a ribbon field momentarily into impressing position upon actuation of any one of said printing control keys, backspace drive means for step-wide moving said paper support mechanism in a backward direction in letter width increments upon successive operations of said backspace drive means, the improvement which comprises means for disabling said spacing means, and a manually operable key operatively connected respectively to said backspace drive means, said ribbon vibrator and said disabling means whereby actuation of said manually operable key will concurrently backspace said paper support mechanism, disable said spacing means to prevent movement of said paper support mechanism and condition said vibrator to move the obliterating field of said ribbon into position to obliterate an imprinted character upon actuation of a printing control key, said spacing means including an escapement and an impeller having a dog and the disabling means including a lever arranged to latch said escapement against movement, a slide member having spaced lugs sequentially engageable by said dog whereby to control the movement of said slide member, cam means associated with said slide member, and means actuated by said cam means to act on said lever to unlatch said escapement to render said spacing means effective.
 3. In a printing apparatus including character printing mechanism, paper support mechanism, spacing means for step-wise moving said paper support mechanism relative to said printing mechanism to accomplish printing a line of characters, and means for disabling said spacing means, said spacing means including an escapement and an impeller having a dog, said disabling means including a lever arranged to latch said escapement against movement, a slide member having spaced lugs sequentially engageable by said dog whereby to control the movement of said slide member, cam means associated with said slide member, and means actuated by said cam means to act on said lever to unlatch said escapement to render said spacing means effective.
 4. In a printing apparatus including character printing mechanism, paper support mechanism, spacing means for step-wise moving said paper support mechanism to accomplish printing a line of characters, and means for disabling said spacing means, said spacing means including an escapement and an impeller having a dog, said disabling means including a lever arranged to latch said escapement against movement, a slide member comprising a plate having a cut out, a flat spring member received in said cut out, said plate and said spring member having spaced upstanding lugs arranged to be sequentially engageable by said dog whereby to control the movement of said slide member in one direction, said spring member being yieldable so as to permit the lugs thereon to pass under said dog in an opposite direction of movement of said slide member.
 5. In an error correcting typewriter comprising character printing mechanism including printing control keys operatively connected to said character printing mechanism, paper support mechanism, spacing means operatively controlled by said printing control keys for step-wise moving said paper support mechanism in a forward direction to accomplish printing of a line of characters, a ribbon providing a printing field and a print obliterating field, a ribbon vibrator actuated by the printing control keys guiding said ribbon to bring a ribbon field momentarily in impressing position, backspace drive means for stepwise moving said paper support mechanism in a backward direction in letter width increments, the imProvement which comprises means for disabling said spacing means to prevent forward movement of said paper support mechanism for two successive actuations of any of said printing control keys, a manually operable key connected with and operable to con-currently operate said backspace drive means, said disabling means and said ribbon vibrator to position the ribbon obliterating field in impressing position, whereby upon the actuation of a first printing control key next following the actuation of said manually operable key a character imprinted in error is obliterated, and means operated by said first printing control key for concurrently conditioning said spacing means and said ribbon vibrator for printing over the obliterated character a correct character upon the actuation of a second printing control key and for rendering said spacing means again effective. 